Thermal Poling of Soda-Lime Silica Glass with Nonblocking Electrodes - Part 2: Effects on Mechanical and Mechanochemical Properties

The mechanical and mechanochemical properties of soda lime silica (SLS) glass surfaces can vary with the sodium ion (Na⁺) concentration in the subsurface region. Changes in these properties were studied upon modification of Na⁺ concentrations in the SLS glass by thermal poling. In Part-1, it is found that the Na⁺-depleted and Na⁺-gradient layers could be formed at the anode and cathode sides, respectively. Here in Part-2, we show that Na⁺ ions play a pivotal role in the mechanochemical wear property upon lateral shear stress. The Na⁺-depleted glass wear more readily as relative humidity (RH) increases, while Na⁺-gradient glass becomes resistant to wear at high RH. It is also found that the Na⁺-gradient glass surface has a higher elastic modulus and hardness with very little change in fracture toughness compared to the pristine surface. The Na⁺-depleted glass surface shows a lower elastic modulus and hardness; but its fracture toughness is significantly improved, which might be due to a larger densification capacity of Na⁺-depleted layer.